Xero Pension submission to NEST

Firstly, let me say that I hate Xero Payroll, but this client has insisted we use it.

All e'ees were manually registered with NEST and previous contribution schedules had been manually uploaded, so this is the first Xero->NEST upload that we've tried. (Reason is that it failed in the past and the staff member deicded that rather than fix the issue she'd sidestep it. Anyway, she's left and I'd prefer to get this linked properly so there's no room for errors.)

I have just tried to submit July's pension report to NEST and of course it's been rejected for 2 reasons:

1. The Xero error report lists the same e'ee twice with the warning IFC02012 (duplicated e'ee). This person was only paid once in the month and is not duplicated on the staff list. I've seen this warning before, when the same NINO had been inputted for 2 different e'ees, which made sense. This does not.

2. Every e'ee has the warning IFC01645 (information doesn't match the schedule). From previous Moneysoft issues, this is normally (always?) if the pay period doesn't match the NEST reference period e.g. calendar month v tax month. I've checked and the Xero pay period (July) matches the NEST schedule period (1 - 31 July).

Xero's list of possible pension rejections lists only 3 possibilities, none of which are the above. Their forum has an unanswered question re IFC01645.

Help. Any ideas?

Thanks